Manual

-46-
You will not be able to find the word NAND in your
d
ictionary (unless it is a computer or electronic
d
ictionary). This term means inverted or Non-AND
function. It creates output conditions that are the
opposite of the AND circuits output conditions.
When both inputs A and B are high the NAND
output is low. If either or both of the inputs are low
then the output is high. The symbol for logic looks
like the AND symbol but with a small circle at the
output. AB is the representation of the function.
The NPN transistor stays off when either or both
terminals A and B are connected to terminal 124
(logic low terminal), and negative current flows
through the diode(s). The LED remains off. Both
diodes allow positive voltage to flow through them
when both of the inputs are connected to terminal
119 (logic high terminal). The NPN transistor is
turned on by positive voltage, thus the current flows
to light the L on the LED.
Notes:
EXPERIMENT #31: “NAND” DTL CIRCUIT WITH DISPLAY
Wiring Sequence:
o 81-20-19-18-119
o 25-47
o 82-46-128-126
o 48-130
o 121-122
o 124-129
o 125-(to 124 “LOW” or 119 “HIGH”)
o 127-(to 124 “LOW” or 119 “HIGH”)
Schematic
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